US2938609A - Automatic adjustor for brakes - Google Patents

Description

May 31, 1960 R. T. BURNETT AUTOMATIC ADJUSTOR FOR BRAKES PRES UEE RELEAJED L LCLEARANCE D" illll|llllllifvll| UNDEK PKESJU INVENTOR. @gcmmo T. BURNETT ATTORNEY AUTOMATIC ADJUSTOR FOR BRAKES Filed Sept. 9, 1954, Ser- No. 455,051 4 Claims. c1. res-1s This invention relates generally to an automatic adjustor and more specifically, to a piston-stroke controlling device for use in a fluid motor. i

The adjustment of axially-applied friction elements, as for example disk brake elements, involves successively spreading the elements apart to compensate for lining wear. Though the width of the lining is worn incidentally to brake usage, it is thus possible to maintain the same clearance between the friction surface and that portion of the brake with which it is engageable. 7

There are a number of deficiencies in adjusting devices with which I am acquainted. These deficiencies involve; complexity of construction, tendency to over adjust,

, and prohibitive cost.

without the use of structure other than that already regarded as essential to the brake; (3) eliminating drag i.e. development of torque while the brake is released; (4) supplying refined degrees of adjustment which do not result in over adjustment of the brake.

These objects and others will become more apparent from a consideration of the following description which proceeds with reference to the accompanying drawings in which:

Figure l is a section view of a fluid motor and brake elements actuated thereby; and

Figure 2 is a schematic illustration of an adjusting operation. The left hand side of Figure 2 shows the piston in extended position, and the right hand side of Figure 2 shows the piston in released position.

Referring to Figure 1, a fluid motor 12 which is carried by brake unit 14 has a pair of pistons 16 slidably received in cylinder bore 18. The pistons are connected through ball-joints 20 to disk friction elements 22.

An annular groove 24 is formed in cylinder bore 18 adjacent either of the opposite ends thereof. O-ring seals 26 are positioned in grooves 24 for exerting a slight rctracting force on the pistons 16.

The inside diameter of the O-ring seal is slightly less than the bore diameter. The pistons compress the inner edge of the O-ring seal thus making a flat annular sealing surface 28 between each piston 16 and its accompanying seal 26. The sealing surface varies somewhat during brake release and brake application as will be apparent from a comparison of sealing surfaces on the right and left hand of Figure 2. The O-ring seal 26 grips the outer periphery of the piston 16 and is capable of movement with the piston 16, which movement is limited by abutment of the seal with opposite sides of the groove 24.

In operation, fluid pressure is introduced to the fluid motor 12 in brake unit 14, spreading the disk ele ments 22 apart, engaging them with axially spaced sides of a rotor (not shown).

When the operator releases applying effort, hydraulic pressure in the fluid motor is diminished sufiiciently to nited States PatfifitO permit retraction of the disk" elements 32 from the sides of the rotor. The retraction of the disk elements is suflicicnt to substantially eliminate any drag on the rotorwhich is not produced by the operators applying efiort. This retracting of the piston is accomplished by means of the resiliency of the O-ring seal 26.

"Referring to Figurei2,' the left hand portion illustrates the condition of the seal when fluid pressure has been developed in the cylinder bore 18 to apply the disk elements 22. The piston 16 is now in extended position. It will be noted that theO-ring seal 26 is deformed against a side of the groove24 which serves as an abutment limiting further movement of theseal with the pistrim. The piston travelfhowever, is limited only by contact of the disk elements with a side of the rotor.

Acertain amount of the energy which produces movement of the piston 16 goes into deforming the resilient d-ring seal 26 so that it assumes the shape illustrated on the left hand side of Figure 2.' When the fluid pressure is released, the resilient seal 26 tends to resume its original shape, depicted on the right hand side of Figure 2. The seal 26 grips the outer periphery of thevpiston 16, and as the seal expands away from the side of the groove 24 it pulls on the piston 16 retracting it through the distance D. distance of retraction D is sufficient to substantially eliminate drag of the disk element 22 on the engaging side of the rotor.

Duringretractivemoveme'nt of the piston 16, there is no relative motion between the seal 26 and the piston 16; thus, the elasticity of the deformed seal '26 is utilized to pull the disk, element 22 away from engagement with the rotor. In this way it is possible to substantially eliminate drag of the brake without'the addition of any components other than those heretofore. regarded as absolute essentials in the brake. f

'The described functionof the.O-ring seal 26 as a return means, makes it possible to maintain constant clearance of the disk element 22 from an applied position irrespective of the extent of wear of the lining on the disk element 22. The piston may be moved sufficiently. to cause complete application of the lining against the side of the rotor, but when the pressure is released, the seal 26 will always return the piston 16 the same amount irrespective of the travel of the piston 16 on its extending stroke. This is an important consideration because it is the distance the disk element moves in being applied that determines the pedal travel required by the operator to fully apply the brake.

By means of the described piston-seal-cylinder construction, pedal travel will not be adversely affected by wear of the lining on the disk elements; and yet, drag of the disk elements on the rotor has been substantially eliminated without foregoing the advantages of free floating pistons.

If the seal-adjustor should position the disk elements responsively to an overheated rotor, then rotor contraction forces the sides thereof to re-engage the lining with a sufliciently great effort to retract the disk elements against the resistance of the O-ring seals; thus over adjustment is compensated for by pushing of the sides of the rotor against the friction surface of the disk element.

Although this invention has been described in connection with a specific embodiment, the principles involved are susceptible of numerous other applications which will occur readily to those persons skilled in the art. I intend to include within the scope of the following claims all equivalent applications of the principles of the invention by which substantially the same results of the invention maybe obtained.

I claim:

1. In a fluid motor, a cylinder, two oppositely-acting nann -applied"disk einehts, a pair at oppositely-ace iiig pistons" 'slidably "received in said" cylinder and operatively connected to said disk elements to provide both protractile and rctractile force thereon, a resilient memser eerifinatwttmn'ieacher' twois acea graeves. at "are der, ea hofi diagrams-havin shoulder a'gainst which'itsse liiig nienieerji fries dwam'said jston bein propernoneq' tofprovide flu'id access 'to the resinem member which" seals the nonndrpisto f surface en;

non 'betweeneaen'sehl and its'ofipo edpiston surface to pressed, two pistons'rceived within said cylinder"'bore and proportioned to"b e' 'of slightly less; diameter than's'aid cylinder bore "to provide aoe ss or fluid pressure to each of said resilient members"whicn-arecempressed against the shoulder as' 'the" fluid motor is energized; mean; 6pera'tively" connecting" each of said'pistons to arespective one of said friction Tmembe'rs, afidag'ri'ppingcofiri'ection between each or said'resil ient niembers'afid"itsf'respective piston 'by which theli'e'silient fmehiberfprovides 'afi'efra'c'tile force on the "piston and-its" connected" friction irimber "when the "resilient fnieniber to fit: "unreli'evedn 3. For use in coiinbir'iitionwith a" pair of oppositelyactirig friction elementsfa cylindrjhaving a c unaer bore termed thereinfapaifofoppositely-acting pistons each having an operative cdnneetibnw'ith a respectiveonebf said friction elements to move'the frictiome'lenienfin each of opposite directions; two resilient sealing members confined; hidividuallyw'ithin each of 'two grooves located adjacent the open ends 'of'said cylinder bore, each of said grooves having 'a shoulder against which the sealing'me'm- 'ber is' compressed, each said resilientmember being" pro- V portioned to extend within the space surrounded by said cylinderbore," said pistons being proportioned to provide fluid access between the piston and its opposed bearing surface of said cylinder bore to act against the resilient member which provides a fluid barrier by deformation against its coacting shoulder, anda gripping connection between each said resilient-member and piston providing retractivet force on the piston and its interconnected friction rfiri'iber as 'tlie"sealreti1i'ns'to i'ts' undeformed state when the pressure in said cylinder is relieved.

T4.'II1'a.'ffiuid" lfiQtOl' aCiuatl for-a laterally applied disk friction element, a cylinder, an annular groove formed in the wall of saidcylinder adjacent the open end thereof, a i'esilieht'mernber cofifincdwithin said groove formed in the cylinder aiid: proportioned of such size that a portion thereof protrudes within the space surrounded by said cylinder bore, a shoulder within said groove against which the resilient member is compressed, a' 'istomi'ece'ived within said cylinder bore and propor- "tiend td-be'r slightly less diametenthan" said cylinder bore to provide access of fluid pressure to said resilient hien rber "which iswn'ipressed against the shoulder as the fluidfirn'otor isferieigizedjmeans 'operatively connecting said piston to said friction member, 'anda gripping connection-betweensaid i'esilient member and said pistonby whichtheresilienf member pro'vides a retractile force on the piston aiid 'i'ts" connected" friction" member when the resilient member retuins to 'its undeformed condition'as manure-pressure is relieved.

: References -Cited'in the file-of this patent UNITED STATES PATENTS ;2;12j0, '9 '2 2 Rninunntnt; June14,i93 2,174,490 j McQ'ine Sept. 26, 1939 1,208,620 Raiser July 23,1940 2,336,352 j Goep'frich "Dec. 7, 1943 2352329 Foi'bes -z- J u1 '4, 1'9f4'4 2358.740 Scott-Ivers en Sept. 19, 1 94 4 237L554 Scott-Ive'rsen Mar. 13, 1945 2,596,298 shrerner May 13,1952 2 ,598,609 Samuel May 27,1952

V-FOREIGN PATENTS 818,889 'Germany Oct. 29, "1951

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